1. Field of the Invention
This invention relates to a lighting device and a display device using the same, and more particularly to a front light and a reflective display.
2. Description of the Prior Art
In FIG. 1, there is shown a sectional view of a conventional reflective liquid crystal display 1. A reflective liquid crystal display 1 is mainly composed of a liquid crystal display 3 and a front light 2 including a light source 4 and a light guide 5.
According to this display 1, the light, emitted from the light source 4, enters the light-entering surface 8 of the light guide 5 and spreads inside the light guide 5. On the upper side of the light guide 5, there are provided flat portions 6 and a plurality of patterns 7 having a first surface 7a and a second surface 7b. Basically, the light that reaches the first surface 7a is reflected thereon to be emitted from the light-emitting surface 9 toward the liquid crystal display 3. The light emitted from the light-emitting surface 9 is reflected by a reflector 13 provided within the liquid crystal display 3 and passes again through the light guide 5 to be emitted outside. Accordingly, the front light 2 illuminates the liquid crystal display 3, and an observer can recognize an image formed by the liquid crystal display 3.
However, with the use of the front light 2 like this, a part of the light that reaches the first surface 7a is not reflected thereon and passes through the first surface 7a. Some of the light that passed through the first surface 7a reaches the second surface 7b and the rest uselessly comes outside directly.
This useless light decreases the rate of the light amount emitted from the light-emitting surface 9 to the light amount emitted from the light source 4, which resultantly deteriorate the brightness and the contrast of the reflective liquid crystal display 1.
In such a case, in order to improve the brightness and the contrast, more light sources are used or a light source that consumes more electricity is used, which increases the manufacturing cost, the consumption of electricity, or the size of a resultant device.
On the other hand, the edges of the patterns 7 formed on the upper surface of the light guide 5 are curved to some extent because it is difficult to form straight boundaries. Accordingly, in case the light, passed through the first surface 7a, reaches the boundary portion, the light is uselessly reflected toward an observer, which makes the image whitish to deteriorate the visibility.